Author: Valter Popeskic

This useful troubleshooting command for cmd provides information about network speed and network loss at every node between a source and destination. Pathping sends Echo Requests to every router between a source and destination and then calculates the results based on the packets returned from every device. By displaying the percentage of packet loss at any given node, we can see which router have some network problems. Pathping is making the same thing like tracert command but with more information about every router on the way.

A firewall in terms of traditional network configurations serves as a default gateway for hosts connecting to one of its secured subnets. A transparent firewall acts like a “stealth firewall” and it is actually a Layer 2 firewall. In order to implement this, the connection of the security equipment is made to same network on both the internal and external ports. However, there is a separate VLAN for each interface.

Now let’s discuss the characteristics of transparent firewall mode:

• Transparent firewall mode supports outside interface and an inside interface.
• The best thing about transparent firewall mode is that it can run in both the single and multiple context modes.
• Instead of routing table lookups the MAC lookups are performed.

We all are familiar with the term ‘firewall’ but majority of us don’t know the source of its origination. It is actually a terminology used for describing a part of automobile that separated the automobile’s interior from the compartment of engine. In the world of network this term is used metaphorically to show the way internal networks are separated from the hazards of external world. With the help of firewalls the networks are divided into various physical networks and as a result of this the occurrence of potential damages can be controlled otherwise these damages can spread to different subnets.

This works in the same way as the original firewalls worked to stop the spreading of a fire.

Internet standard MIME is able to extend the e-mail format for the purpose to support the following things as text, non-text attachment, a message organization with manifold parts and non-ASCII header information. The existence of MIME protocol has become very important because SMTP as basic e-mail transmission protocol can support only 7-bit of ASCII characters set. But MIME as Presentation layer protocol can hold up 8-bit binary content by describing the ways of sending certain types of data via an electronic mail.

We can protect our voice network with simple Auxiliary VLAN but sometimes to be more secure Auxiliary VLAN are not enough. In this case we can use Security appliances such firewalls or VPN termination devices or both.

Firewall maybe seems like very clean and simple mechanism to protect RTP protocols transmitted voice packets but there’s a problem. Protecting voice networks with a firewall is not so simple because we are not sure what UDP port will be used by the RTP voice packets flow.

If we look at some Cisco network architecture and Cisco device environment, a UDP port for an RTP stream is an random port selected from the pool of 16,384 to 32,767. We surely don’t want to open all those ports on firewall just to be sure that the VoIP will function well. So many open ports may be seen from other side like a bunch of security holes.